As known from the art, light emitting diodes (LEDs) have been used as backlight for displays and illumination panels for some time, where a large number of low power LEDs are arranged in an array. LEDs are well suited for this purpose for several reasons. They are, for instance, durable structures with a long lifetime, which reduces the maintenance needed. Also, they have low power consumption and are operated at lower voltages, which reduce costs of operation and risks related to high voltage applications. In relation to this they have a high light output.